Physical Sciences and Mathematics Commons^™

Dynamic Interplay Between Spacecraft Charging, Space Environment Interactions And Evolving Materials, Jr Dennison

Journal Articles

While the effects on spacecraft charging from varying environmental conditions and from the selection of different construction materials have been studied extensively, modification of materials properties by exposure to the space plasma environment can also have profound effects on spacecraft charging. Given the increasingly demanding nature of space missions, there is a clear need to extend our understanding of the dynamic nature of material properties that affect spacecraft charging and to expand our knowledgebase of materials’ responses to specific environmental conditions so that we can more reliably predict the long term response of spacecraft to their environment. This paper focuses …

Electrostatic Discharge And Endurance Time Measurements Of Spacecraft Materials: A Defect-Driven Dynamic Model, Allen Andersen, Jr Dennison, Alec Sim, Charles Sim

Journal Articles

Electrostatic breakdown leads to the majority of anomalies and failures attributed to spacecraft interactions with the plasma space environment. It is therefore critical to understand how electrostatic field strength (F_ESD) of spacecraft materials varies due to environmental conditions such as duration of applied electric field, rate of field change, history of exposure to high fields, and temperature. We have developed a dual-defect, thermodynamic, mean-field trapping model in terms of recoverable and irrecoverable defect modes to predict probabilities of breakdown. Fits to a variety of measurements of the dependence of F_ESD of insulating polymers on endurance time, voltage …

Electrical Properties Study Under Electron Beam Of Annealed And Coated Boron Nitride, Kevin Guerch, Thierry Paulmier, Jr Dennison, Justin Dekany, Sophie Guillemet-Fritsch, Pascal Lenormand

Journal Articles

The charging and relaxation kinetics of pyrolytic boron nitride (BN) substrates, BN with an aluminum oxide (BN/Al₂O₃) coating, and thermally-annealed alumina-coated boron nitride (an–BN/Al₂O₃) were investigated under low power electron irradiation (5 < incident energy E₀ < 20 keV and incident flux J_i = 10 nA.cm^-2 at room temperature) in the CEDRE facility at ONERA (Toulouse, France). Surface potentials of each ceramics configuration were measured over time using the Kelvin probe method. The influence of coating and annealing treatments to limit charging is discussed in this paper. A thorough study of a an–BN/Al₂O₃ sample was carried out …

Radar Detection Of Ultra High Energy Cosmic Rays: Searching For Coincident Events With Telescope Array Radar And Surface Detectors, Zachary Gibson, Rasha Abbasi, John Belz

Presentations

No abstract provided.

The Simulation & Evaluation Of Surge Hazard Using A Response Surface Method In The New York Bight, Michael H. Bredesen

UNF Graduate Theses and Dissertations

Atmospheric features, such as tropical cyclones, act as a driving mechanism for many of the major hazards affecting coastal areas around the world. Accurate and efficient quantification of tropical cyclone surge hazard is essential to the development of resilient coastal communities, particularly given continued sea level trend concerns. Recent major tropical cyclones that have impacted the northeastern portion of the United States have resulted in devastating flooding in New York City, the most densely populated city in the US. As a part of national effort to re-evaluate coastal inundation hazards, the Federal Emergency Management Agency used the Joint Probability Method …

Integrating Security Into The Undergraduate Software Engineering Curriculum, Robert Evans

UNF Graduate Theses and Dissertations

This research included a thorough examination of the existing software assurance or what is commonly called software security knowledge, methodologies and what information security technologies is currently being recommended by the information technology community. Finally it is demonstrated how this security knowledge could be incorporated into the curriculum for undergraduate software engineering.

Mobile Cloud Computing: Offloading Mobile Processing To The Cloud, Jesus Zambrano

UNF Graduate Theses and Dissertations

The current proliferation of mobile systems, such as smart phones, PDA and tablets, has led to their adoption as the primary computing platforms for many users. This trend suggests that designers will continue to aim towards the convergence of functionality on a single mobile device. However, this convergence penalizes the mobile system in computational resources such as processor speed, memory consumption, disk capacity, as well as in weight, size, ergonomics and the user’s most important component, battery life. Therefore, this current trend aims towards the efficient and effective use of its hardware and software components. Hence, energy consumption and response …

Comparing Group Means When Nonresponse Rates Differ, Gabriela M. Stegmann

UNF Graduate Theses and Dissertations

Missing data bias results if adjustments are not made accordingly. This thesis addresses this issue by exploring a scenario where data is missing at random depending on a covariate x. Four methods for comparing groups while adjusting for missingness are explored by conducting simulations: independent samples t-test with predicted mean stratification, independent samples t-test with response propensity stratification, independent samples t-test with response propensity weighting, and an analysis of covariance. Results show that independent samples t-test with response propensity weighting and analysis of covariance can appropriately adjust for bias. ANCOVA is the stronger method when …

Sorting By Block Moves, Jici Huang

UNF Graduate Theses and Dissertations

The research in this thesis is focused on the problem of Block Sorting, which has applications in Computational Biology and in Optical Character Recognition (OCR). A block in a permutation is a maximal sequence of consecutive elements that are also consecutive in the identity permutation. BLOCK SORTING is the process of transforming an arbitrary permutation to the identity permutation through a sequence of block moves. Given an arbitrary permutation π and an integer m, the Block Sorting Problem, or the problem of deciding whether the transformation can be accomplished in at most m block moves has been shown to be …

Characterization Of A Biosynthetic Pathway Yielding Anticancer Natural Products From A Marine Bacterium, Elle D. James

UNF Graduate Theses and Dissertations

Natural products are bioactive secondary metabolites produced by living organisms and are prevalently utilized as pharmaceutical drugs. Marine adapted organisms are a promising source of new natural products possessing unique chemical structures and biological activities. By studying the biosynthetic pathways employed by living organisms to produce natural products, insights into new strategies to generate molecules to combat disease and overcome drug resistance may be gained. This thesis study aimed to uncover the biosynthetic pathway employed by a marine actinomycete, Nocardiopsis sp. CMB-M0232, to catalyze the assembly of the nocardioazines. These molecules are a group of 2,5-diketopiperazine natural products that feature …

Time Series Similarity Search In Distributed Key-Value Data Stores Using R-Trees, Aleksey Charapko

UNF Graduate Theses and Dissertations

Time series data are sequences of data points collected at certain time intervals. The advance in mobile and sensor technologies has led to rapid growth in the available amount of time series data. The ability to search large time series data sets can be extremely useful in many applications. In healthcare, a system monitoring vital signals can perform a search against the past data and identify possible health threatening conditions. In engineering, a system can analyze performances of complicated equipment and identify possible failure situations or needs of maintenance based on historical data.

Existing search methods for time series data …

Infinite Product Representations For Kernels And Iteration Of Functions, Daniel Alpay, Palle Jorgensen, Izchak Lewkowicz, Itzik Marziano

Mathematics, Physics, and Computer Science Faculty Articles and Research

We study infinite products of reproducing kernels with view to their use in dynamics (of iterated function systems), in harmonic analysis, and in stochastic processes. On the way, we construct a new family of representations of the Cuntz relations. Then, using these representations we associate a fixed filled Julia set with a Hilbert space. This is based on analysis and conformal geometry of a fixed rational mapping R in one complex variable, and its iterations.

Boundary Interpolation For Slice Hyperholomorphic Schur Functions, Khaled Abu-Ghanem, Daniel Alpay, Fabrizio Colombo, David P. Kimsey, Irene Sabadini

Mathematics, Physics, and Computer Science Faculty Articles and Research

A boundary Nevanlinna-Pick interpolation problem is posed and solved in the quaternionic setting. Given nonnegative real numbers κ1,…,κN, quaternions p1,…,pN all of modulus 1, so that the 2-spheres determined by each point do not intersect and pu≠1 for u=1,…,N, and quaternions s1,…,sN, we wish to find a slice hyperholomorphic Schur function s so that
limr→1r∈(0,1)s(rpu)=suforu=1,…,N,
and
limr→1r∈(0,1)1−s(rpu)su¯¯¯¯¯1−r≤κu,foru=1,…,N.
Our arguments relies on the theory of slice hyperholomorphic functions and reproducing kernel Hilbert spaces.

Inner Product Spaces And Krein Spaces In The Quaternionic Setting, Daniel Alpay, Fabrizio Colombo, Irene Sabadini

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper we provide a study of quaternionic inner product spaces. This includes ortho-complemented subspaces, fundamental decompositions as well as a number of results of topological nature. Our main purpose is to show that a closed uniformly positive subspace in a quaternionic Krein space is ortho-complemented, and this leads to our choice of the results presented in the paper.

Spectral Theory For Gaussian Processes: Reproducing Kernels, Random Functions, Boundaries, And L2-Wavelet Generators With Fractional Scales, Daniel Alpay

Mathematics, Physics, and Computer Science Faculty Articles and Research

A recurrent theme in functional analysis is the interplay between the theory of positive definite functions, and their reproducing kernels, on the one hand, and Gaussian stochastic processes, on the other. This central theme is motivated by a host of applications, e.g., in mathematical physics, and in stochastic differential equations, and their use in financial models. In this paper, we show that, for three classes of cases in the correspondence, it is possible to obtain explicit formulas which are amenable to computations of the respective Gaussian stochastic processes. For achieving this, we first develop two functional analytic tools. They are: …

Defining Terms: Greywater, Blackwater And Clearwater, Roslynn Brain, Jeremy Lynch, Kelly Kopp

Natural Resources

Why irrigate with treated drinking water when you can meet your irrigation needs through an effective greywater system?

What is greywater*? Greywater includes all wastewater generated in the home, except toilet water (which is considered “blackwater”). In Utah, kitchen sink and dishwasher water are also categorized as “blackwater”. Greywater is an abundant resource in both residential and commercial buildings. According to Brad Lancaster of the Watershed Management Group in Tucson, Arizona, “greywater harvesting is the practice of directing greywater to the primary root zone (top 2 feet or 0.6m of the soil) of perennial plants to help grow beautiful and …

Determinantal Ideals From Symmetrized Skew Tableaux, Bill Robinson

Theses and Dissertations--Mathematics

We study a class of determinantal ideals called skew tableau ideals, which are generated by t x t minors in a subset of a symmetric matrix of indeterminates. The initial ideals have been studied in the 2 x 2 case by Corso, Nagel, Petrovic and Yuen. Using liaison techniques, we have extended their results to include the original determinantal ideals in the 2 x 2 case, as well as special cases of the ideals in the t x t case. In particular, for any skew tableau ideal of this form, we have defined an elementary biliaison between it and one …

Role Of Antenna Modes And Field Enhancement In Second Harmonic Generation From Dipole Nanoantennas, Domenico De Ceglia, Maria Antonietta Vincenti, Costantino De Angelis, Andrea Locatelli, Joseph W. Haus, Michael Scalora

Electro-Optics and Photonics Faculty Publications

We study optical second harmonic generation from metallic dipole antennas with narrow gaps. Enhancement of the fundamental-frequency field in the gap region plays a marginal role on conversion efficiency. In the symmetric configuration, i.e., with the gap located at the center of the antenna axis, reducing gap size induces a significant red-shift of the maximum conversion efficiency peak. Either enhancement or inhibition of second-harmonic emission may be observed as gap size is decreased, depending on the antenna mode excited at the harmonic frequency. The second-harmonic signal is extremely sensitive to the asymmetry introduced by gap’s displacements with respect to the …

Nonlinear Hierarchical Models For Longitudinal Experimental Infection Studies, Michael David Singleton

Theses and Dissertations--Epidemiology and Biostatistics

Experimental infection (EI) studies, involving the intentional inoculation of animal or human subjects with an infectious agent under controlled conditions, have a long history in infectious disease research. Longitudinal infection response data often arise in EI studies designed to demonstrate vaccine efficacy, explore disease etiology, pathogenesis and transmission, or understand the host immune response to infection. Viral loads, antibody titers, symptom scores and body temperature are a few of the outcome variables commonly studied. Longitudinal EI data are inherently nonlinear, often with single-peaked response trajectories with a common pre- and post-infection baseline. Such data are frequently analyzed with statistical methods …

Singular Value Computation And Subspace Clustering, Qiao Liang

Theses and Dissertations--Mathematics

In this dissertation we discuss two problems. In the first part, we consider the problem of computing a few extreme eigenvalues of a symmetric definite generalized eigenvalue problem or a few extreme singular values of a large and sparse matrix. The standard method of choice of computing a few extreme eigenvalues of a large symmetric matrix is the Lanczos or the implicitly restarted Lanczos method. These methods usually employ a shift-and-invert transformation to accelerate the speed of convergence, which is not practical for truly large problems. With this in mind, Golub and Ye proposes an inverse-free preconditioned Krylov subspace method, …

Extension Of Chebfun To Periodic Functions, Grady B. Wright, Mohsin Javed, Hadrien Montanelli, Lloyd N. Trefethen

Mathematics Faculty Publications and Presentations

Algorithms and underlying mathematics are presented for numerical computation with periodic functions via approximations to machine precision by trigonometric polynomials, including the solution of linear and nonlinear periodic ordinary differential equations. Differences from the nonperiodic Chebyshev case are highlighted.

Identifying Similar Polygons: Comparing Prospective Teachers’ Routines With A Mathematician’S, Sasha Wang

Mathematics Faculty Publications and Presentations

This paper reports two prospective teachers' and a mathematician's ways of identifying similar triangle and hexagons through the analysis of routines, a characteristic of geometric discourse. The findings show that visual recognition was a common approach for the mathematician as wells as the two prospective teachers. However, when asked for justification, their routines of identifying similar polygons diverged. The paper also discusses the implication of classroom discourse practices to enhance prospective teachers' communication and reasoning skills while learning geometric concepts such as similarity.

Dynamics Of Climate Change: Explaining Glacier Retreat Mathematically, Robert Guillette

Undergraduate Review

Climate change is an important topic that has become extremely relevant this day and age. The world’s climate is undergoing monumental shifts with over two-thirds of the estimated 150 glaciers existing in 1850 disappearing by 1980. The melting of glaciers offers tangible evidence of broader environmental changes as they respond directly to long-term trends in temperature, precipitation, and solar radiation. Since the study of glacier retreat provides a barometer of climate change, it is important to better understand the effects of climatic factors on glaciers. In my project I created a mathematical model for the melting of glaciers and used …

Natural Language Processing For Foreign Language Learning, Jacob Kausler

Honors Theses

This research presents novel algorithms which generate sentences in a natural language, using natural language generation techniques. The purpose of the algorithms is to benefit foreign language learning. As far as we can tell, ours is the first such research being done in the field. In creating the algorithms, we also developed a piece of software to showcase the work and allow testing by users. The main algorithm begins by generating sentence models by using one of two methods, namely modeled sentence generation and semantic sentence generation. Each of these have benefits and drawbacks, which the user must take into …

On The Capacitance Of Crystalline Silicon Solar Cells In Steady State, Fabe Idrissa Barro, Moustapha Sane, Bernard Zouma

Turkish Journal of Physics

In this work, an analytical approach is presented for modeling the capacitance of crystalline silicon solar cells. Based on a one-dimensional modeling of the cell, the excess minority carrier density, the photovoltage, and the capacitance are calculated. The motivation of this work are two-fold: to show base doping density and illumination effects on the capacitance of silicon solar cells, and to propose a determination technique for both dark capacitance and base doping density from C-V characteristics.

Evaluation Of The Global Solar Irradiance In The Vhembe District Of Limpopo Province, South Africa, Using Different Theoretical Modelsevaluation Of The Global Solar Irradiance In The Vhembe District Of Limpopo Province, South Africa, Using Different Theoretical Models, Tshimangadzo Sophie Mulaudzi, Nnditshedzeni Eric Maluta, Vaith Sankaran

Turkish Journal of Physics

An attempt has been made to employ three different theoretical models for the determination of global solar radiation for the climate conditions of the Vhembe district of Limpopo Province in South Africa. The models are: 1) the Angstrom linear-based model, 2) the Hargreaves and Samani (temperature-based) model, and 3) the Garcia model. These models require the following meteorological data inputs: temperature, sunshine hours, and global solar irradiance on the horizontal surface. The regression coefficients from our previous study were also employed in the calculations. A 4-year (2007--2010) global solar irradiance and temperature data set from the Agricultural Research Council and …

Nanocrystalline Nio Structure: Preferred Oriented Growthnanocrystalline Nio Structure: Preferred Oriented Growth, Ali Rahmati, Soheila Mardani

Turkish Journal of Physics

Nickel oxide (NiO) nanostructures were deposited on Si (100), potassium bromide (KBr), and glass slide substrates at room temperature by the evaporation technique. The prepared samples were annealed at temperatures of 400 $^{\circ}$C and 600 $^{\circ}$C in air atmosphere. The structure, morphology, crystalline phase, optical properties, and chemical bonding of nanocrystalline nickel oxide were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible absorption spectrum, and FT-IR spectroscopy. XRD results and SEM images showed that nickel oxide nanoparticles have preferred orientation with uniform size distribution. The as-deposited films showed preferred orientation (texture) growth. As the films were annealed, the …

External Magnetic Field Effect On Bifacial Silicon Solar Cell''S Electric Power And Conversion Efficiencyexternal Magnetic Field Effect On Bifacial Silicon Solar Cell''S Electric Power And Conversion Efficiency, Issa Zerbo, Martial Zoungrana, Idrissa Sourabie, Adama Ouedraogo, Bernard Zouma, Dieudonne Joseph Bathiebo

Turkish Journal of Physics

This article presents a modelling study of external magnetic field effect on a bifacial silicon solar cell's electric power and conversion efficiency. After the resolution of the magnetotransport equation and continuity equation of excess minority carriers, we calculate the photocurrent density and the photovoltage and then we deduce the solar cell's electric power before discussing the influence of the magnetic field on those electrical parameters. Using the electric power curves versus junction dynamic velocity we determine the maximum electric power, the operating point of the solar cell, and the conversion efficiency according to magnetic field intensity. The numerical data show …

Wind, Waves And Surge: An Analysis Of The Movement And Post-Storm Recovery Of Bushy Point Beach In Groton, Ct, Grace Medley

Physics, Astronomy and Geophysics Honors Papers

Barrier beaches are highly dynamic systems that respond to variations in wave energy, increases in storm surge heights and changes in relative sea level. Bushy Point barrier beach is a barrier spit located in Groton, Connecticut, and is one of the last unconstrained barrier systems in the State of Connecticut. Since 1934, the morphology of the beach has been changing in response to storm events as well as the local rise in sea level. On September 21, 1938, a category three hurricane made landfall in southern New England and devastated many coastal communities, including a summer community on Bushy Point …

Isabel Stafford Presents Research To National Security Agency, Lucero Castellanos-Aguirre

Lake Union Herald

No abstract provided.